Window wells can fill with water because of negative watershed adjacent to them.  The water actually enters the well from the sides and up from the bottom but not often from the top as many people believe.

Window well covers are a good option as they can prevent water entering from a gutter overflow and leaves collecting in them.  By removing the old window well, adding fresh gravel and creating positive slope, we can solve the mystery of window wells leaking.  In some cases, French drains must be installed to draw the water away from the window well and foundation wall, however, these must be deeper than the window sill and flow by gravity to daylite at the discharge point.

Interior drain tiles, sump pumps and holes drilled through your foundation wall to drain the outside water into your basement then pump it back out is not advised in most circumstances.